This invention is an improvement over the particle blasting system described in U.S. Pat. No. 4,038,786 entitled "Sandblasting With Pellets of Material Capable of Sublimation" and assigned to the assignor of this invention. In that patent a system was described for blasting with solid carbon dioxide particles to clean, for example, various different types of surfaces of various different types of contaminants. The advantages of using solid carbon dioxide particles is that there is no resultant cleaning up of the particles after blasting and essentially no atmospheric contamination. As described further in such patent, numerous problems have been encountered in the use of dry ice particles for blasting purposes. The problems recited relate generally to a limited density of the particle, rounded edge and corner configurations of such a particle and non-uniformity of the blasting stream because of particle feed variations due to agglomeration. While these problems were generally solved by the teachings of such patent, nonetheless other problems arose which caused the system to operate less than satisfactory. These problems related to insufficient velocity of the particles in the gas stream, non-uniformity and breaking of particles, back up and insufficient feed of particles into the gas stream and freezing incurring in the area of the feed mechanism and the nozzle.
Accordingly, it is a general object of the present invention to provide a blasting machine utilizing particles of material capable of sublimation.
It is another object of the present invention to provide a blasting machine for sublimable particles which is capable of imparting a high velocity to the particles without causing damage to the particles.
It is a further object of the present invention to provide a blasting machine for sublimable particles which can provide a high volume of particles into a low pressure, high velocity gas flow.
It is still another object of the present invention to provide a blasting machine for sublimable particles which can easily provide particles having a substantially uniform length.
It is a further object of the present invention to provide a blasting machine in which the temperature of the gas flow into the feed mechanism and the nozzle is regulated to prevent freezing in such regions and to assist in the acceleration of the particles.